Miniature passive thermal control valve for mixing or splitting single-phase fluid with adjustable thermal actuator

ABSTRACT

A passive thermal control valve comprising a thermal actuator coupled to a valve body having first and second ports. The thermal actuator including an actuator body having an inner bore. An adjustment stop engages the actuator body. A cylinder is received within the actuator body inner bore and the cylinder has a cylinder bore open at one end. An actuator spring within the actuator body biases the cylinder towards the adjustment stop. An actuator rod is at least partially received within the cylinder and has first and second ends. At least a portion of the actuator rod is allowed to extend through the open cylinder bore. A sealing element forms a seal between the actuator rod and the cylinder and defines a sealed chamber within the cylinder. A thermal fluid is contained within the cylinder. A lever mechanism is connected to the valve body and includes a lever having a first end connected to the valve body. A valve spool is connected to a lever second end. The valve spool is arranged and designed to close the first port and allow a system fluid to flow through the second port, close the second port and allow the system fluid to flow through the first port, or allow the system fluid to flow through both the first and second ports.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application Ser. No. 63/360,049 filed on Aug. 30, 2021. Applicant incorporates by reference herein Application Ser. No. 63/360,049 in its entirety.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

This invention was made with Government support under Contract No. 80NSSC21C0239, awarded by NASA (National Aeronautics and Space Administration) Shared Services Center (NSSC). The Government therefore has certain rights in this invention.

BACKGROUND OF THE INVENTION 1 Field of the Invention

The present invention relates generally to a thermal control valve, more particularly to a miniature passive thermal control valve having an adjustable thermal actuator, and even more particularly to a miniature passive thermal control valve for mixing or splitting single-phase fluid having an adjustable thermal actuator.

2 Description of the Related Art

Passive thermal control valve assemblies are known in the art. Such assemblies do not require a power source, such as a battery or DC power supply to operate. The thermal control valve includes a thermal actuator that actuates in response to the change in temperature of the system fluid. The motion is typically a linear movement of a rod within a cylinder of an actuator housing. A temperature-sensing material sealed within the cylinder expands and contracts based on the temperature of the device. The temperature-sensing material can be a liquid or wax-like substance or any other material that changes volume based on the temperature range anticipated by the actuator.

When the temperature-sensing material experiences a temperature increase, the substance expands in volume. The expansion pushes against the rod forcing the rod to extend out of the cylinder. When the temperature of the temperature-sensing material cools, the volume of the substance contracts which pulls the rod inside the cylinder.

Thermal actuators have certain advantages compared to more conventional solutions. A conventional solution would be to provide a solenoid, temperature sensor, electronic control circuitry, and a battery or DC power supply. A thermal actuator inside of a thermal control valve enables it to operate as a single device that integrates temperature sensing, actuating and fluid control functions. Thus, a number of external components are eliminated.

Since the passive thermal control valve does not require a supply of electricity, the device is immune to power failures. Passive thermal control valve assemblies are compact, lightweight units that offer safe, reliable operation in hazardous or extreme environment applications. For example, such assemblies have been used in aerospace, satellite, and outer space applications. The passive thermal control valve assemblies are often used with Loop Heat Pipes (LHPs). LHPs are versatile heat transfer devices that have been used for thermal control of many commercial communications satellites and NASA’s spacecraft and rovers. A 2012 article published by American Institute of Aeronautics and Astronautics describing this is entitled “Passive Control of a Loop Heat Pipe with Thermal Control Valve for Lunar Lander Application,” authors John R Hartenstine, Kara L. Walker, and William G. Anderson, Advanced Cooling Technologies, Inc., Lancaster, PA 17601.

Prior thermal control valves typically used a linear valve approach which required large spool travel that increased the size of the valve. Additionally, prior thermal control valves were designed to operate for a larger temperature control range than currently desired and had lower flow rate ratings. The prior thermal control valve would be large, bulky and would take up too much volumetric space if designed to meet the current desired specifications.

It is desired to have a thermal control valve that operates within a tighter temperature control range with higher accuracy and over a wide range of ambient temperature extremes than currently exists. It is also desirable that the thermal control valve has increased flow rate capacity and up to double the flow rate of the existing state-of-the-art thermal control valve. It is further desired that the thermal control valve have a reduced size up to one half the size and weight of existing state-of-the-art thermal control valve assemblies. It would also be desirable to have a miniature passive three-way thermal control valve that can operate as either a mixing valve (i.e., having two liquid inlet ports and one liquid outlet port) or a splitting valve (i.e., having one liquid inlet port and two liquid outlet ports). Such miniature passive thermal control valves could find use in a number of single-phase mechanically pumped fluid thermal control systems and operate within a smaller temperature control range than the existing state-of-the-art valves.

SUMMARY OF THE INVENTION

The present invention is thermal control valve that operates within a tighter temperature control range with higher accuracy and over a wide range of ambient temperature extremes than currently exists. The thermal control valve has increased flow rate and up to double the flow rate of existing state-of-the-art thermal control valve assemblies. The thermal control valve has a reduced size up to approximately one half the size and weight of existing state-of-the-art thermal control valve assemblies. Additionally, the miniature passive three-way thermal control valve that can operate as either a mixing valve (i.e., having two liquid inlet ports- and one liquid outlet port) or a splitting valve (i.e., having one liquid inlet port and two liquid outlet ports).

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

The aspects, features, and advantages of the embodiments of the invention mentioned above are described in more detail by reference to the drawings, wherein like reference numerals represent like elements having the same basic function, in which:

FIG. 1 is a sectional view of a passive thermal control valve according to an embodiment of the present invention with a lever mechanism and valve spool in an upper position;

FIG. 1A is an enlarged view of the valve of FIG. 1 with the lever mechanism and valve spool in the upper position;

FIG. 2 is a view similar to FIG. 1 showing the fluid flow path through the splitting thermal control valve;

FIG. 3 is a sectional view of the embodiment of the adjustable thermal actuator shown in FIGS. 1 and 2 , the adjustable thermal actuator being O-ring sealed;

FIG. 3A is an enlarged view of an end portion of the O-ring sealed adjustable thermal actuator;

FIGS. 4A to 4E show the O-ring sealed adjustable thermal actuator and positions of the actuator rod and actuator cylinder at different actuator fluid temperatures when an adjustment stop is set for a lower extreme temperature control range;

FIGS. 5A to 5D show the O-ring sealed adjustable thermal actuator and positions of the actuator rod and actuator cylinder at different actuator fluid temperatures when the adjustment stop is set for an upper extreme temperature control range;

FIG. 6 is a sectional view of the passive thermal control valve according to a second embodiment of the present invention having a bellows sealed adjustable thermal actuator and with the lever mechanism and spool in a lower position;

FIG. 6A is an enlarged view of a portion of the actuator of FIG. 6 ; and

FIG. 7 is a perspective view of a preferred embodiment of the spool body.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

It should be understood at the outset that although illustrative implementations of one or more embodiments are described below, the disclosed assemblies, systems and methods may be implemented using any number of techniques, whether currently known or not yet in existence. The disclosure should in no way be limited to the illustrative implementations, drawings, and techniques described below, but may be modified within the scope of the appended claims along with their full scope of equivalents.

The following brief definition of terms shall apply throughout the application:

The phrases “in one embodiment,” “according to one embodiment,” and the like generally mean that the particular feature, structure, or characteristic following the phrase may be included in at least one embodiment of the present invention, and may be included in more than one embodiment of the present invention (importantly, such phrases do not necessarily refer to the same embodiment);

If the specification describes something as “exemplary” or an “example,” it should be understood that refers to a non-exclusive example;

The terms “about” or “approximately” or the like, when used with a number, may mean that specific number, or alternatively, a range in proximity to the specific number, as understood by persons of skill in the field of the art;

If the specification states a component or feature “may,” “can,” “could,” “should,” “would,” “preferably,” “possibly,” “typically,” “optionally,” “for example,” “often,” or “might” (or other such language) be included or have a characteristic, that particular component or feature is not required to be included or to have the characteristic. Such component or feature may be optionally included in some embodiment, or it may be excluded.

Embodiments of the invention will now be described with reference to thefigures, in which like numerals reflect like elements throughout. The terminology used in the description presented herein is not intended to be interpreted in any restrictive or limited way, simply because it is being utilized in conjunction with the detailed description of certain specific embodiments of the invention. Furthermore, embodiments of the invention may include several novel features, no single one of which is solely responsible for its desirable attributes or which is essential to practicing the invention described herein.

A preferred embodiment of the passive thermal control valve, generally referred to as 100, will now be described with respect to FIGS. 1, 1A, 2, 3 and 3A. FIG. 2 shows the flow path of a system fluid F through a splitting valve configuration. The splitting valve configuration has one inlet port IP and two outlet ports OP-1 and OP-2. It is to be understood that when the system fluid flow directions are reversed from those shown in FIG. 2 , the passive thermal control valve 100 operates as a mixing valve with OP-1 and OP-2 becoming first and second inlet ports and IP becoming a single outlet port.

The passive thermal control valve 100 comprises a thermal actuator 10 having an actuator body 12, actuator spring 14, actuator cylinder 16, actuator rod 18 and adjustment stop 20 as shown in FIGS. 1 and 2 . Referring to FIG. 1 , the actuator body 12 includes an inner bore 12 b and a lower interior shoulder 12 s. The actuator spring 14 fits within the inner bore 12 b and has a first end 14 f that abuts the lower interior shoulder 12 s of the actuator body 12.

Referring to FIGS. 3 and 3A, the actuator cylinder 16 has a bore 16 b at a top end 16 t sized to receive the actuator rod 18. An O-ring 22 received in a cylinder groove 16 g forms a seal between the actuator rod 18 and actuator cylinder 16 to form a sealed chamber 16 c within the actuator cylinder 16. A thermal or actuator fluid 24 is provided in the sealed chamber 16 c as will be discussed in greater detail below. The O-ring 22 separates the actuator fluid 24 from the system fluid F as shown in FIG. 2 .

As best shown in FIG. 3A, the actuator cylinder 16 preferably includes an exterior flange 16 f at the top end 16 t. The exterior flange 16 f is arranged and designed to abut a second end 14 s of the actuator spring 14. The exterior flange 16 f also includes a plurality of ports 16 p providing passageways for the system fluid F.

Still referring to FIG. 3A, the adjustment stop 20 preferably has a central bore 20 b and an exterior threaded portion 20 t for engaging an interior threaded portion 12 t of the inner bore 12 b of the actuator body 12. The central bore 20 b is sized to receive the actuator rod 18. The adjustment stop 20 also includes a plurality of passageways 20 p to allow the system fluid F to flow through the adjustment stop 20. An exterior threaded locknut 26 threadably engages the inner bore 12 b of the actuator body 12 and locks the position of the adjustment stop 20 as will be discussed below.

Referring to FIGS. 1 and 1A, a valve body 30 is mounted to the actuator body 12 of the thermal actuator 10, preferably via a threaded connection. A lever mechanism 32 within the valve body 30 includes a lever 34, a lever pin 36, an upper stop 38, a lower stop 40, a lever spring 42, and a spool pin 44. Referring to FIG. 1A, the lever 34 has a pin hole 34 h adjacent to one end of the lever 34 and a spool receiver 34 r at an opposite end of the lever 34 adapted to receive a valve spool 50.

It is to be understood that the lever 34 is pin-supported to the valve body 30 via the lever pin 36. Various techniques may be used. Although not shown, one example is a pair of plates mounted within the valve body 30 and spaced to allow the lever 34 to freely fit between the plates with the plates having an aligned hole for receiving the lever pin 36. With the lever pin hole 34 h aligned between the hole of the plates, the lever pin 36 is inserted through the aligned holes and the lever 34 is allowed to partially rotate about the lever pin 36. It is to be understood that other techniques may be used to allow the lever 34 to partially rotate about the lever pin 36.

Although not fully shown in FIG. 1A, the spool receiver 34 r may be a U-shaped member having an arcuate portion joined to a pair of straight leg portions. An aligned spool pin opening extends through each of the straight leg portions of the spool receiver 34 r and the valve spool 50 includes a spool opening 50 o (FIGS. 1A and 7 ) through which the spool pin 44 extends.

It is to be understood that the valve body 30 may have one or more openings for assembling the lever mechanism 32 and valve spool 50.

As shown in FIG. 1 , preferably the actuator rod 18 has a first end 18 f received within the actuator cylinder 16 and a second end 18 s outside of the cylinder 16 and which may contact the lever 34, preferably a concave surface 34 c (FIG. 1A) of the lever 34. Preferably, the second end 18 s of the actuator rod 18 is a spherical cap. In the preferred embodiment, the spherical cap contacts the lever concave surface 34 c in a point contact. Also in the preferred embodiment, line contact is made between the lever pin 36 and the lever 34 and between the lever 34 and the spool pin 44.

Referring to FIG. 1A, the upper stop 38 may include a cylindrical lower portion 38 c received within the valve body 30 and receiving the lever spring 42. The lever spring 42 may have one end piloted on the lever 34. The lever spring 42 is in compression and exerts a spring force on the lever 34.

Referring to FIGS. 1, 1A, 2 and 7 , the preferred embodiment of the valve spool 50 will be described in greater detail. The valve body 30 includes an upper spool guide 30 a and a lower spool guide 30 b as shown in FIG. 1A. A portion of the valve spool 50 is always within the upper and lower spool guides 30 a and 30 b. The preferred embodiment of the valve spool 50 is a fluted spool having a plurality of flutes 52 along the circumference of the spool 50. The fluted spool profile is shown in FIG. 1A. The spool 50 has an upper portion 50 a and a lower portion 50 b separated by a medial portion 50 c. The medial portion 50 c includes the opening 50 o for receiving the spool pin 44. The upper portion 50 a includes a plurality of flutes 52 and the lower portion includes a plurality of flutes 52. The valve spool 50 is a cylindrical body that is interrupted by the plurality of flutes 52. Preferably, the flutes 52 terminate towards the medial portion 50 c and the spool 50 transitions to an uninterrupted circular cylindrical portion 50 u.

When the lever 34 is against the upper stop 38 and the spool 50 is in the upper position as shown in FIG. 1A, the uninterrupted circular cylindrical portion 50 u of the valve spool 50 is received within the spool guide 30 a. Due to a tight clearance between the spool guide 30 a and the uninterrupted circular cylindrical portion 50 u, the leakage is very small and fluid flow to the first outlet port OP-1 is effectively closed. Similarly, when the lever 34 is against the lower stop 40 and the spool 50 is in the lower position as shown in FIG. 6 , the uninterrupted circular cylindrical portion 50 u of the valve spool 50 is received within the spool guide 30 b and fluid flow to the second outlet port OP-2 is effectively closed.

Each flute 52 is generally scoop-shaped beginning narrow and shallow adjacent the uninterrupted circular cylindrical portion 50 u and gradually becoming wider and deeper along the length of the flute 52. The fluted profile is designed to provide linear trim characteristics through the plurality of flutes 52 along the circumference of the spool 50. The fluted profile is a seat guided design which allows for a tighter clearance between the spool 50 and the spool guides 30 a and 30 b of the valve body 30 which helps to reduce leakage when the port is closed. Additionally, the seat guided design reduces the axial length of the valve body 30 which reduces the size and weight of the thermal control valve 100.

The assembly, installation, and operation of an embodiment of the thermal actuator 10 will now be described in detail with reference to FIGS. 4A-4E and 5A-5D. It is to be understood that in FIGS. 4A-4E, the adjustment stop 20 of the thermal actuator 10 is set for a temperature control range of -55° C. to -48° C. (a lower extreme temperature control range), whereas in FIGS. 5A-5D the adjustment stop 20 is set for a temperature control range of 83° C. to 90° C., which is a higher extreme temperature control range. The control range is the temperature range in which the spool transition will occur from one port to the other. It is to be further understood that the adjustment stop 20 may be adjusted to other positions within the actuator body 12 for other temperature control ranges.

With reference to FIG. 4A, a predetermined volume of the actuator fluid 24 at room temperature is added to the sealed chamber 16 c of the actuator cylinder 16. The position of the actuator rod 18 inside the cylinder 16 in FIG. 4A is based on the predetermined volume of room temperature actuator fluid 24 added to the sealed chamber 16 c. Preferably, the entire volume of the sealed chamber 16 c is filled with the actuator fluid 24 and a portion of the actuator rod 18.

The actuator spring 14 is positioned in the actuator body 12 with the spring first end 14 f contacting the interior shoulder 12 s of the actuator body 12. Although not shown, it is to be understood that the actuator spring 14 has a spring free length in a relaxed state. In the preferred embodiment, the free length of the actuator spring 14 is greater than the distance from the lower interior shoulder 12 s of the actuator body 12 (FIG. 1 ) to an upper end 12 u of the actuator body 12 (FIG. 3A). The filled actuator cylinder 16 and actuator rod 18 may be inserted into the actuator spring 14 within the actuator body 12 until the spring second end 14 s contacts the exterior flange 16 f of the cylinder 16.

An actuator spring preload will be determined based on the setting of the adjustment stop 20. For the -55° C. to -48° C. temperature control range setting shown in FIG. 4A, the compression of the actuator spring 14 at room temperature will provide a minimum required preload.

With the second end 18 s of the actuator rod 18 extending through the central bore 20 b of the adjustment stop 20, the adjustment stop 20 may be brought into contact with the upper portion of the actuator cylinder 16 to compress the actuator spring 14 prior to threading the adjustment stop 20 to the actuator body 12. Preferably, the actuator cylinder 16 is forcibly pushed down via the actuator rod 18, as for example by hand, to a position below the desired adjustment stop position, further compressing the actuator spring 14. The adjustment stop 20 may then be threaded into the actuator body 12 to the desired adjustment stop position shown in FIGS. 4A-4E. The downward force on the actuator rod 18 may be removed and the actuator spring 14 urges the actuator cylinder 16 into contact with the adjustment stop 20. The locknut 26 may then be threaded into the actuator body 12 until it contacts the adjustment stop 20 and locks the position of the adjustment stop 20.

FIG. 4B shows the position of the actuator cylinder 16 and rod 18 when the actuator assembly 10 is installed on the valve body 30 at room temperature. When the actuator assembly 10 is connected to the valve body 30, preferably via a threaded connection, the actuator rod 18 will push the lever 34 against the upper stop 38 of the valve 100 compressing the lever spring 42 (see FIG. 1A). Since the actuator rod 18 cannot be pushed inside the actuator cylinder 16 due to the incompressible actuator fluid 24, the actuator cylinder 16 will slide down within the actuator body 12, further compressing the actuator spring 14. The actuator fluid 24 is still at room temperature and the pressure inside the actuator cylinder 16 will be equivalent to the actuator spring load.

FIG. 4C shows the position of the actuator rod 18 and cylinder 16 at the actuator fluid temperature of -48° C. (i.e., the upper limit control range temperature). As the actuator fluid temperature decreases from the room temperature to the upper limit control range temperature of -48° C., the volume of the actuator fluid 24 will decrease. To compensate for the reduction in actuator fluid volume, the actuator cylinder 16 will retract until it contacts the adjustment stop 20 as shown in FIG. 4C.

As the temperature of the actuator fluid 24 decreases from room temperature to the upper limit control range of -48° C. as illustrated in FIGS. 4B and 4C, the volume of actuator fluid decreases, the cylinder 16 retracts to the adjustment stop 20, the length of the rod 18 within the cylinder 16 increases, and the actuator spring 14 becomes less compressed. It is to be understood that over the entire temperature range from room temperature to -48° C., the second end 18 s of the rod 18 has remained in the same position. The position is shown in FIGS. 1A, 4B and 4C. As shown in FIG. 1A, the actuator rod 18 forces the lever 34 against the upper stop 38 and the spool 50 is positioned such that the second outlet port OP-2 is open.

FIG. 4D shows the position of the actuator rod 18 and cylinder 16 at the actuator fluid temperature of -55° C. (i.e., the lower limit control range temperature). As the actuator fluid temperature further decreases from the upper limit control range temperature (-48° C.) to the lower limit control range temperature (-55° C.), the actuator fluid volume further decreases. To compensate for the reduction in the actuator fluid volume, the actuator rod 18 will retract within the cylinder 16 and obtain the position shown in FIG. 4D. As the rod 18 retracts within the cylinder 16, the second end 18 s moves to the lower control range position and the lever spring 42 expands and forces the valve spool 50 to the lower position shown in FIG. 6 in which the lever 34 contacts the lower stop 40 and the first outlet port OP-1 is open.

It is to be understood that when the temperature of the actuator fluid 24 is -51.5° C. (i.e., midway between the upper and lower limit control range temperatures), the rod 18 assumes a position midway between the positions shown in FIGS. 4C and 4D and the lever 34 is at a midstroke position such that first and second inlet ports OP-1 and OP-2 are equally open (i.e., open the same amount).

FIG. 4E shows the position of the actuator rod 18 and cylinder 16 at the actuator fluid temperature of 125° C. (i.e., the maximum rated temperature of the valve 100). The actuator rod 18 will be at the upper control range rod position and the position of the valve spool 50 will be such that the second outlet port OP-2 will be open. At this stage, the actuator rod 18 pushes the lever 34 against the upper stop 38 which restricts further travel of the lever 34 and valve spool 50. The actuator rod 18 is restricted from further travel towards the upper stop 38 for any increase in actuator fluid temperature beyond the upper limit control range temperature. To compensate for the increase in the actuator fluid volume due to temperature rise from the upper limit control range temperature up to 125° C., the actuator cylinder 16 will move away from the adjustment stop 20, compressing the actuator spring 14 and will obtain the position shown in FIG. 4E.

FIGS. 5A-5D show the thermal actuator 10 set for a temperature control range of 83° C. to 90° C., which is a higher extreme temperature control range of the valve 100. Functioning of the thermal actuator 10 at this control range setting is similar to the one discussed above.

FIG. 5A shows the adjustment stop 20 in the actuator assembly 10 set for the temperature control range of 83° C. to 90° C. As described above, the actuator fluid 24 in the actuator cylinder 16 is filled at room temperature and the position of the actuator rod 18 inside the cylinder 16 will be determined based on the required actuator fluid volume at the room temperature. The preload of the actuator spring 14 will be determined based on the adjustment stop setting. At 83° C. to 90° C. control range, the actuator spring compression will provide a substantial required preload. As shown in FIG. 5A, the actuator cylinder 16 is in contact with the adjustment stop 20.

FIG. 5A shows the position of the actuator cylinder 16 and rod 18 when the actuator assembly 10 is assembled and installed on the valve body 30 at room temperature. At room temperature, a portion of the actuator rod 18 extends through the adjustment stop 20 but does not extend beyond the upper end 12 u of the actuator body 12 and into the valve body 30. The position of the actuator rod 18 is based on the predetermined amount of required actuator fluid 24.

FIG. 5B shows the position of the actuator rod 18 and cylinder 16 at the actuator fluid temperature of 83° C. (lower limit control range temperature). As the temperature of the actuator fluid 24 increases from room temperature to the lower limit control range temperature, the volume of the actuator fluid 24 increases. The increased volume of actuator fluid 24 pushes more of the actuator rod 18 out of the actuator cylinder 16. The second end 18 s of the actuator rod 18 will assume the lower control range lever position as shown in FIG. 5B. Preferably, the actuator cylinder 16 remains in contact with the adjustment stop 20 at this temperature as a result of the actuator spring force.

FIG. 5C shows the position of the actuator rod 18 and cylinder 16 at the actuator fluid temperature of 90° C. (upper limit control range temperature). As the actuator fluid temperature further increases from the lower limit control range temperature (83° C.) to the upper limit control range temperature (90° C.), the actuator fluid volume further increases. To compensate for the increase in the actuator fluid volume, the actuator rod 18 will extend further out of the actuator cylinder 16 and obtain the upper control range lever position shown in FIG. 5C. The actuator rod 18 will stroke from the lower limit control range temperature (83° C.) to the upper limit control range temperature (90° C.) which will actuate the valve spool 50 and the spool position will change from the first outlet port OP-1 being open to the second outlet port OP-2 being open. At this stage, the actuator rod 18 will push the lever 34 against the upper stop 38 which will restrict further travel of the lever 34 and the valve spool 50. The actuator rod 18 is restricted from further travel towards the upper stop 38 for any increase in actuator fluid temperature beyond the upper control range temperature. Preferably, the actuator cylinder 16 remains in contact with the adjustment stop at this temperature as a result of the actuator spring force.

FIG. 5D shows the actuator rod 18 and cylinder 16 positions at the actuator fluid temperature of 125° C. (maximum rated temperature of the valve 100). As the actuator fluid temperature increases from the upper control range temperature to 125° C., the actuator fluid volume increases. To compensate for this increase in the actuator fluid volume, the actuator cylinder 16 will move away from the adjustment stop 20 compressing the actuator spring 14 further and will obtain the position shown in FIG. 5D.

FIG. 6 shows a second embodiment of the passive thermal control valve, designated as 100’. In this second embodiment the valve body 30, lever mechanism 32, upper and lower stops 38 and 40, and valve spool 50 are the same but the thermal actuator 110 has a bellows 122 as opposed to the O-ring sealed design described above. The working principal of both thermal actuators 10 and 110 is the same. The primary difference between the two embodiments is the way the system fluid F and the actuator fluid 24 are isolated from each other. In the bellows sealed thermal actuator 110, the bellows 122 separates the actuator fluid 24 from the system fluid F.

With reference to FIG. 6 , the thermal actuator 110 includes an actuator body 112, actuator spring 114, actuator cylinder 116, adjustment stop 120, locknut 126 and actuator/thermal fluid 24. It is to be understood that these components are similar to the components described above with respect to the O-ring sealed thermal actuator 10. A first end 122 f of the bellows 122 is sealingly affixed, preferably by welding, to a first end 118 f of the bellows rod 118. A second end 122 s of the bellows 122 is affixed to a top flange 116 f of the cylinder 116. As the bellows 122 compresses, the bellows rod 118 is pushed outward.

The thermal fluid 24 is between the bellows 122 and the cylinder 116. The system fluid F is between the actuator body 112 and the cylinder 116 and also between the bellows 122 and the rod 118 as there is a clearance between the rod 118 and the top flange 116 f which allows system fluid F to enter.

It is to be understood that the bellows sealed thermal actuator 110 functions similarly to the O-ring sealed thermal actuator 10. The above discussion relating to FIGS. 4A-4E and 5A-5D also pertain to the bellows sealed thermal actuator 110.

In the splitting configuration, the working fluid F enters the valve 100, 100' through a single inlet port IP and the outlet flow is split between two outlet ports OP-1 and OP-2 based on the position of the valve spool 50.

The linear thermal control valve 100, 100' includes a linear thermal actuator 10, 110 that strokes in response to a change in temperature of the working fluid F and has a lever mechanism 32 that amplifies the linear stroke of the thermal actuator 10, 110 and actuates the spool 50, with the spool controlling the system fluid flow based on its linear position in the valve body 30. This design significantly reduces the linear stroke requirement of the thermal actuator 10, 110 compared to existing thermal control valves because of the stroke amplification achieved by the lever mechanism 32.

A suitable system fluid F is Fluorinert® Electronic Liquid FC-72, a product of 3M Company, and a suitable actuator fluid is Dow Corning® 200. The O-ring 22 may be made of EPDM (Ethylene Propylene Diene Monomer) elastomer which is suitable for the discussed temperature ranges. Additionally, EPDM is compatible with the system fluid (FC-72) and the actuator fluid (DC-200). A suitable material for the actuator rod and adjustment stop is silicon bronze (C65100) and 304 Stainless Steel for the actuator cylinder, actuator body, locknut, and actuator spring.

It is to be understood that the thermal actuator 10, 110 in the preferred embodiments actuates the valve spool 50 via the lever mechanism 32. The lever mechanism 32 amplifies the actuator stroke and provides a longer stroke at the valve spool 50. This results in a smaller actuator stroke for a given spool stroke. The smaller actuator stroke requires less actuator fluid volume which further reduces the size and weight of the thermal control valve 100, 100'. In existing state-of-the-art thermal control valves, the thermal actuator is in-line with the spool axis which does not provide the stroke amplification benefit of the preferred embodiments of the present invention.

It is to be understood that the actuator/bellows rod 18, 118 of the thermal actuator 10, 110 in the preferred embodiments will stroke only during the temperature change that occurs within the set control range. For any temperature increase outside of the set control range, the actuator cylinder 16, 116 will extend instead of the actuator rod 18, 118 to accommodate expansion in the actuator fluid volume. Since the travel of the actuator rod 18, 118 is fixed, the spool 50 connected to the actuator rod 18, 118 via the lever mechanism 32 will also have a fixed travel. This eliminates the spool stroking beyond the set temperature control range which significantly reduces the axial length and weight of the thermal control valve 100, 100'. In existing state-of-the-art thermal control valves, the spool travel is equal to the total actuator stroke because the spool is directly connected to the actuator rod. The total axial length of existing state-of-the-art thermal control valves is a multiplier of the total actuator stroke, which makes the valve bigger and heavier.

Additional benefits and advantages of the preferred embodiments of the present invention include the following.

1) The thermal fluid expansion during the temperature change outside of the control range is accommodated inside the actuator 10, 110 instead of continuing to move or put force on the spool 50.

2) The actuator stroke length for a fixed spool stroke is much smaller because of the amplification provided by the lever mechanism 32, which reduces the size of the actuator and the valve.

3) The extension of the actuator cylinder 16, 116 to compensate for the changing thermal fluid volume is much smaller because of the smaller actuator stroke, which reduces the size of the actuator and the valve.

4) The length of the valve body 30 is reduced by combining the flow passages with the spool guide 30 a, 30 b.

5) The valve spool 50 has fluted scoops and a conical shape that goes into the spool guide 30 a, 30 b to decrease the flow at a controlled rate and providing a linear flow transition.

6) The actuator and flow path are combined to further reduce space.

Nomenclature List

-   system fluid F -   inlet port IP -   first outlet port OP-1 -   second outlet port OP-2 -   thermal actuator 10 -   actuator body 12 -   inner bore 12 b -   interior shoulder 12 s -   interior threaded portion 12 t -   upper end 12 u -   actuator spring 14 -   first end 14 f -   second end 14 s -   actuator cylinder 16 -   bore 16 b -   sealed chamber 16 c -   exterior flange 16 f -   cylinder groove 16 g -   ports 16 p -   top end 16 t -   actuator rod 18 -   first end 18 f -   second end 18 s -   adjustment stop 20 -   central bore 20 b -   passageways 20 p -   exterior threaded portion 20 t -   O-ring 22 -   thermal/actuator fluid 24 -   locknut 26 -   valve body 30 -   upper spool guide 30 a -   lower spool guide 30 b -   lever mechanism 32 -   lever 34 -   concave surface 34 c -   pin hole 34 h -   spool receiver 34 r -   lever pin 36 -   upper stop 38 -   cylindrical portion 38 c -   lower stop 40 -   lever spring 42 -   spool pin 44 -   valve spool 50 -   upper portion 50 a -   lower portion 50 b -   medial portion 50 c. -   opening 50 o -   uninterrupted circular cylindrical portion 50 u -   flutes 52 -   passive thermal control valve 100, 100' -   thermal actuator 110 -   actuator body 112 -   actuator spring 114 -   actuator cylinder 116 -   top flange 116 f -   bellows rod 118 -   first end 118 f -   adjustment stop 120 -   bellows 122 -   first end 122 f -   second end 122 s -   locknut 126

The foregoing disclosure and description of the invention are illustrative and explanatory thereof, and various changes in the size, shape and materials, as well as in the details of the illustrated construction, may be made without departing from the spirit of the invention. The present embodiments are, therefore, to be considered as merely illustrative and not restrictive, the scope of the invention being indicated by the claims rather than the foregoing description, and all changes which come within the meaning and range of equivalence of the claims are therefore intended to be embraced therein.

While the invention has been described in detail above with reference to specific embodiments, it will be understood that modifications and alterations in the embodiments disclosed may be made by those practiced in the art without departing from the spirit and scope of the invention. All such modifications and alterations are intended to be covered. In addition, all publications cited herein are indicative of the level of skill in the art and are hereby incorporated by reference in their entirety as if each had been individually incorporated by reference and fully set forth. 

We claim:
 1. A passive thermal control valve comprising: a thermal actuator comprising: an actuator body having an inner bore; an adjustment stop engaging the actuator body; a cylinder received within the inner bore of the actuator body, the cylinder having a cylinder bore open at one end; an actuator spring within the actuator body biasing the cylinder towards the adjustment stop; an actuator rod having a first end and a second end, the actuator rod at least partially received within the cylinder, at least a portion of the actuator rod allowed to extend through the open cylinder bore; a sealing element forming a seal between the actuator rod and the cylinder and defining a sealed chamber within the cylinder; and a thermal fluid contained within the cylinder; and a valve body coupled to the actuator body, the valve body having first and second ports; a lever mechanism connected to the valve body, the lever mechanism comprising a lever having first and second ends and a medial portion, the lever first end pin-connected to the valve body; a valve spool connected to the lever second end, the valve spool arranged and designed to close the first port and allow a system fluid to flow through the second port, close the second port and allow the system fluid to flow through the first port, or allow the system fluid to flow through both the first and second ports.
 2. The passive thermal control valve of claim 1, wherein the adjustment stop engages an upper portion of the actuator body.
 3. The passive thermal control valve of claim 1, wherein the adjustment stop engages an upper portion of the actuator body via threads.
 4. The passive thermal control valve of claim 1, wherein the position of the adjustment stop relative to the actuator body is adjustable.
 5. The passive thermal control valve of claim 4, wherein the adjustment stop threadably engages the actuator body.
 6. The passive thermal control valve of claim 1, wherein the second end of the actuator rod is allowed to contact the lever and position the lever between a lower position and an upper position.
 7. The passive thermal control valve of claim 6, wherein the valve spool closes the second port when the lever is in the lower position.
 8. The passive thermal control valve of claim 7, wherein the valve spool closes the first port when the lever is in the upper position.
 9. The passive thermal control valve of claim 6, further comprising: an upper stop in the valve body, the upper stop limiting upward movement of the lever and defining the upper position of the lever; and a lower stop in the valve body, the lower stop limiting downward movement of the lever and defining the lower position of the lever.
 10. The passive thermal control valve of claim 9, wherein the upper and lower stops limit the axial movement of the valve spool.
 11. The passive thermal control valve of claim 1, wherein the actuator body has an actuator body port at a lower end of the actuator body and the actuator body is coupled to the valve body at an upper end of the actuator body.
 12. The passive thermal control valve of claim 11, wherein the first and second ports of the valve body are first and second outlet ports and the actuator body port is an inlet port for the system fluid.
 13. The passive thermal control valve of claim 12, further comprising a system fluid flow path from the inlet port to the first and second outlet ports.
 14. The passive thermal control valve of claim 13, wherein the system fluid flow path comprises an area in the inner bore of the actuator body outside of the cylinder and into the valve body to the first and second outlet ports.
 15. The passive thermal control valve of claim 11, wherein the first and second ports of the valve body are first and second inlet ports and the actuator body port is an outlet port for the system fluid.
 16. The passive thermal control valve of claim 15, further comprising a system fluid flow path from the first and second inlet ports to the outlet port.
 17. The passive thermal control valve of claim 16, wherein the system fluid flow path comprises an area in the inner bore of the actuator body outside of the cylinder and into the valve body to the first and second outlet ports.
 18. The passive thermal control valve of claim 1, wherein the valve body includes an upper spool guide and a lower spool guide, and the valve spool comprises an upper portion and a lower portion separated by a medial portion, the upper and lower portions each having a plurality of flutes along a circumference of the valve spool, at least a portion of the upper portion of the valve spool is in the upper spool guide and at least a portion of the lower portion of the valve spool is in the lower spool guide.
 19. The passive thermal control valve of claim 18, wherein each flute is generally scoop-shaped beginning narrow and shallow adjacent the medial portion and gradually becoming wider and deeper along the length of the flute.
 20. The passive thermal control valve of claim 19, wherein the axial positioning of the plurality of flutes within the upper spool guide controls the flow rate of the system fluid through the first port and provides a linear flow transition.
 21. The passive thermal control valve of claim 6, wherein the actuator rod actuates the valve spool via the lever mechanism, and wherein the actuator rod has a rod stroke required to move the lever between the lever upper and lower positions, and the valve spool has a spool stroke required to move from closing the spool body first port to closing the spool body second port, and the lever mechanism amplifies the rod stroke to provide a longer spool stroke.
 22. The passive thermal control valve of claim 9, wherein the valve spool transitions between a lower spool position in which the second port is closed to an upper spool position in which the first port is closed over a temperature control range, the temperature control range defined by an upper control range temperature and a lower control range temperature, wherein at the lower control range temperature the valve spool is in the lower spool position and the lever is in the lever lower position, wherein as the temperature rises above the lower control range temperature, the thermal fluid within the cylinder expands, forcing the actuator rod to push on the lever and raise it from the lever lower position which raises the valve spool from the lower spool position, and wherein at the upper control range temperature the thermal fluid within the cylinder has expanded to force the actuator rod to push on the lever and raise it to the lever upper position which positions the valve spool in the upper spool position.
 23. The passive thermal control valve of claim 22, wherein as the temperature of the thermal fluid exceeds the upper control range temperature, the thermal expansion of the thermal fluid forces the cylinder in a direction away from the adjustment stop, further compressing the actuator spring.
 24. A passive thermal control valve comprising: a thermal actuator comprising: an actuator body having an inner bore; an adjustment stop engaging the actuator body; a cylinder received within the inner bore of the actuator body, the cylinder having a cylinder bore open at one end; an actuator spring within the actuator body biasing the cylinder towards the adjustment stop; a rod having a first end and a second end, the rod at least partially received within the cylinder, at least a portion of the rod allowed to extend through the open cylinder bore; a bellows within the cylinder extending over a portion of the rod, a bellows first end sealingly affixed to a first end of the rod and a bellows second end affixed to a top flange of the cylinder; and a thermal fluid contained within the cylinder on the outside of the bellows; and a valve body coupled to the actuator body, the valve body having first and second ports; a lever mechanism connected to the valve body, the lever mechanism comprising a lever having first and second ends and a medial portion, the lever first end pin-connected to the valve body; a valve spool connected to the lever second end, the valve spool arranged and designed to close the first port and allow a system fluid to flow through the second port, close the second port and allow the system fluid to flow through the first port, or allow the system fluid to flow through both the first and second ports.
 25. The passive thermal control valve of claim 24, wherein system fluid occupies the space inside the bellows. 